The invention is based on an overpressure valve for packaging containers as defined hereinafter. An overpressure valve of this type and its method of production are known from German Patent Publication DE-A 29 31 850. The overpressure valves, which are circular in contour, are detachably glued on a backing strip. The disadvantage of this is the large amount of waste produced when the overpressure valves are punched out of the composite strip. Moreover, a backing strip that additionally increases production costs is necessary for handling or transporting the overpressure valves. Further, a device for attaching overpressure valves to packaging containers is known from European Patent Disclosure EP-A 0 043 425, with which the overpressure valves supplied on a supply roll and glued to the backing strip are detached individually from the backing strip and attached to the packaging container by their adhesive-coated underside. The disadvantage of this is that the backing strips must be collected separately and disposed of.